Pathological changes induced by repeated percutaneous transluminal coronary angioplasty

Metabolic Pathway Genes Associated with Susceptibility Genes to Coronary Artery Disease

Coronary artery disease (CAD) is one of the leading threats to global health. Previous research has proven that metabolic pathway disorders, such as high blood lipids and diabetes, are one of the risk factors that mostly cause CAD. However, the crosstalk between metabolic pathways and CAD was mostly studied on physiology processes by analyzing a single gene function. A canonical correlation analysis was used to identify the metabolic pathways, which were integrated as a unit to coexpress with CAD susceptibility genes, and to resolve additional metabolic factors that are related to CAD. Seven pathways, including citrate cycle, ubiquinone, terpenoid quinone biosynthesis, and N-glycan biosynthesis, were identified as an integrated unit coexpressed with CAD genes. These pathways could not be revealed as a coexpressed pathway through traditional methods as each single gene has weak correlation. Furthermore, sets of genes in these pathways were candidate markers for diagnosis and detection from patients' serum.

Late loss in a disappearing frame of reference: is it still applicable to fully absorbable scaffolds?

Bioabsorbable stents are an important advancement in stent technology providing a temporary scaffold and may be augmented with drugs to suppress neointimal hyperplasia.Though changes are being made to the design of the stents, to ensure similar rates of acute recoil, residual stenosis postintervention remains higher when compared to contemporary durable stents. In order to achieve similar clinical restenosis outcomes, bioabsorbable stents must first show similar MLD or percent diameter stenosis at follow-up to drug-eluting stents.While variable different acute gain and post-procedure MLD for bioabsorbable stents make late lumen loss a poor marker for restenosis probability by itself, late loss can be an informative metric for neointimal hyperplasia over time in these stents.Metrics which are independent of acute gain such as minimal luminal diameter and percentage diameter stenosis may make better surrogates for restenosis (Table 1). Moreover, remodelling over time requires measurement of the vessel and lumen diameters in later follow-up. Since the natural history of the vascular response to bioabsorbable stents is in its infancy of investigation, follow-up of these stents at least beyond the duration of polymer is prudent. Finally, given a disappearing frame of reference, both careful angiographic and intravascular ultrasound assessments are helpful to delineate the varying contributions of recoil, remodelling, and neointima formation.

Successful treatment of intimal hyperplasia in renal arteries by endovascular brachytherapy

PURPOSE

The present study shows the possibility of preventing restenosis of renal arteries by endovascular brachytherapy.

METHODS AND MATERIALS

We present a patient suffering from rapid restenosis of both renal arteries with decreasing renal function. Percutaneous transluminal angioplasty (PTA) and stent implantation were unable to stop hypertension and to stabilize renal function. Both renal arteries and the right pole artery were treated by endovascular brachytherapy in one session.

RESULTS

Six months after intervention, intraarterial digital subtraction angiography (DSA) showed no evidence of recurrence, and the blood pressure remained normal without medical treatment.

CONCLUSION

Endovascular brachytherapy can help to prevent restenosis in renal arteries. It is possible to treat both renal arteries and one pole artery in one session without any disadvantage.

Plaque inflammation in restenotic coronary lesions of patients with stable or unstable angina

OBJECTIVES

To evaluate immunohistochemically various parameters of inflammation in coronary atherectomy specimens obtained from restenotic culprit lesions of patients presenting with either stable or unstable angina (UA).

BACKGROUND

There is no information regarding the relationship between atherosclerotic plaque inflammation and the severity of the coronary syndromes in patients with restenotic coronary lesions.

METHODS

A total of 37 patients with either stable angina or UA underwent directional coronary atherectomy for restenotic coronary lesions. Cryostat sections of atherectomy specimen were immunohistochemically stained with monoclonal antibodies CD68 (macrophages [MACs]), CD3 (T-lymphocytes) and alpha-actin (smooth muscle cells [SMCs]). Smooth muscle cell contents and MAC contents were planimetrically quantified as the percentage immunopositive tissue area of the total tissue area. T-lymphocytes were counted at 100-X magnification throughout the entire section and expressed as number of cells per mm2.

RESULTS

Restenotic coronary lesions of patients with UA or stable angina showed no significant difference in SMC areas (31.9%+/-16.3% vs. 38.5%+/-18.8%, respectively; p = NS). However, restenotic coronary lesions of patients presenting with unstable angina contained significantly more MACs (24.4%+/-15.1% vs. 10.5%+/-5.8%, p = 0.001) and T-lymphocytes (18.8 cells/mm2+/-15.1 cells/mm2 vs. 8.6 cells/mm2+/-9.8 cells/mm2; p = 0.034) than patients with stable angina.

CONCLUSIONS

These results suggested that inflammation appears to affect plaque instability in restenotic coronary lesions resulting in unstable coronary syndromes.

Short- and long-term evolution of unstented nonocclusive coronary dissection after coronary angioplasty

OBJECTIVES

We assessed the short- and long-term clinical and angiographic outcome of nonocclusive unstented dissection after percutaneous transluminal coronary angioplasty (PTCA) and its correlation with restenosis.

BACKGROUND

The use of stents has dramatically increased both the number and the cost of coronary revascularization procedures. However, this technique is not completely risk free, and its benefits have not been fully demonstrated in uncomplicated dissections.

METHODS

We studied 129 consecutive patients with 49 nonocclusive dissections after PTCA (grades A to D of National Heart, Lung, and Blood Institute classification) and good distal flow (TIMI [Thrombolysis in Myocardial Infarction] flow grade 3). All patients underwent coronary angiography at 24 h and at six months post-PTCA. Clinical status was assessed every three months in the outpatient clinic. Study subjects were matched with 60 other patients in whom stenting was performed for the presence of dissection.

RESULTS

In the former group, all but two patients (with type E dissection, which evolved to coronary occlusion and myocardial infarction) improved their dissection score during follow-up: at six months only 18 dissections were still angiographically visible, and no clinical adverse events were recorded. In the dissected vessels, the restenosis rate was significantly lower than in those without dissection (12% vs. 44%, p < 0.001); in the stented vessels, the restenosis rate was 25% (15/60).

CONCLUSIONS

In the presence of TIMI flow grade 3, coronary dissection is associated with a favorable outcome and predicts a low restenosis rate. These results caution against the indiscriminate use of intravascular prostheses in the event of nonocclusive coronary dissection.

Vascular smooth muscle cell outgrowth, proliferation, and apoptosis in young and old rats

We attempted to identify the effects of aging on the response of vascular smooth muscle cells (VSMCs) to injury. Rat aortas were injured by ballooning, and cell outgrowth of the aortic explants, as well as cell proliferation and apoptosis induced by 7-ketocholesterol in the culture system were compared in young (6-7 weeks) and old (40-50 weeks) rats. Explant outgrowth in uninjured rats did not differ between young and old rats. However, 14 days after balloon injury, the number of explants with outgrowth increased by a factor of four (P<0.01) in young rats, while that of the old rats did not change. Cell proliferation in cultured VSMCs also did not differ between young and old uninjured rats, but, in the injured group, proliferation doubled in young rats (P<0.01), but did not change in the older group. The rate of unadhered cells in the presence of 7-ketocholesterol (30 microM) did not differ between young and old uninjured rats. In the injured rats, however, that of young rats was lower (P<0.01) while that of older rats was higher (P<0.01). The extent of DNA fragmentation (%) after the addition of 7-ketocholesterol (30 microM) did not differ between young and old uninjured rats. In the injured groups, DNA fragmentation was lower in the young rats (P<0.01), and higher in the old ones (P<0.01), when compared to their respective controls. These results indicate that the VSMC injury responses of cell outgrowth and proliferation were more pronounced in the young, and that 7-ketocholesterol-induced apoptosis was more extensive in old rats.

The kinase inhibitor fasudil (HA-1077) reduces intimal hyperplasia through inhibiting migration and enhancing cell loss of vascular smooth muscle cells

Smooth muscle cell (SMC) migration plays an important role in restenosis after angioplasty. Myosin phosphorylation is necessary for cell migration. Fasudil is an inhibitor of protein kinases, including myosin light chain kinase and Rho associated kinase, thereby inhibiting myosin phosphorylation, and it has been clinically used to prevent vasospasm following subarachnoid hemorrage. Based on these findings, we examined the anti-migrative action of fasudil. In SMC (SM-3), fasudil (1-100 microM) inhibited SMC migration in a dose-dependent manner (p < 0.001). Fasudil suppressed actin stress fiber formation dose dependently. In rabbit carotid artery, fasudil (10 mg/kg/day) markedly reduced intimal hyperplasia 14 days following balloon injury. Cell kinetic study showed that fasudil did not affect proliferation but enhanced cell loss in the media after injury. We concluded that fasudil reduced neointimal formation after balloon injury through both inhibiting migration and enhancing cell loss of medial SMC.

Brachytherapy with iridium-192 HDR to prevent from restenosis in peripheral arteries. An update

The use of stents does not appreciably improve restenosis (usually resulting from intimal hyperplasia) as compared to percutaneous transluminal angioplasty (PTA) alone. The development of small-caliber probes for afterloading therapy in the biliary tract allowed us to use these for therapy in the vascular system. Using a special 9 F catheter, exact measurement of the length of the stented vascular segment and of the insertion length of the afterloading probe could be reproducibly performed. We used a Nucletron (Micro) Selectron HDR planning system version 10.10 for exact calculation, monitoring, and control of the afterloading procedure. Our source was iridium 192 (10 Ci) with a diameter of 1.1 mm. The program controls and monitors the insertion and removal of the iridium probe from the source into the special catheter through to the tip, and monitors the irradiation duration. The exposure time was around 200 seconds for a surface dose of 12 Gy. To date, a total of 40 patients have been treated with endovascular afterloading. All patients suffered from clinically relevant reocclusions or restenoses in stented vascular segments of the superficial femoral artery following successful PTA or laser treatment, within 6 to 8 months after the last therapy. In all patients it was possible to perform re-PTA treatment without remaining residual stenoses in the stented region. The additional time required as compared to PTA alone was approximately 45 minutes with most of this time spending for transportation between the cath lab and afterloading room. The follow-up period of the 40 patients ranged from 4 months to 71/2 years. In 33 patients, there was no deterioration of the clinical stage and no restenosis. One patient suffered from an acute thrombosis approximately 3 months after stent implantation, another patient had a stenosis 3 cm above the stented vascular segment 12 months after irradiation treatment. Follow-up examinations have revealed no evidence of nerve lesions following irradiation therapy. The tissue surrounding the artery showed no change following irradiation therapy, either in the CT, color-coded Doppler, endovascular ultrasonic scan or MRI. No complaints of discomfort were reported during or after irradiation. With the exceptions mentioned above, there was no evidence of any complications.

The Watanabe heritable hyperlipidemic rabbit is a suitable experimental model to study differences in tissue response between intimal and medical injury after balloon angioplasty

The study evaluates whether the Watanabe heritable hyperlipidemic (WHHL) rabbit is an adequate model to study mechanisms that underlie differences in tissue response after postangioplasty injury. Postangioplasty studies of human coronary arteries have revealed that healing and restenotic processes differ depending on whether the laceration is limited to the atherosclerotic plaque or whether injury extends into the media. Forty-five homozygous WHHL rabbits underwent percutaneous transluminal angioplasty of the left subclavian artery. The inflated arterial segment was studied histologically at 3, 7, 14, 28, and 56 days, using conventional and immunohistochemical techniques to identify macrophages, smooth muscle cell (SMC) phenotypes, and cell proliferation. Electron microscopy was done to study reendothelialization. There were marked differences in response between those segments with medial injury and those with injury limited to the atherosclerotic plaque tissues. The latter category shows a distinct retardation in redifferentiation of SMCs, confirming previous observations in human coronary arteries. In these segments, moreover, cell proliferation occurred mainly in macrophages and spindle cells. Medial injury showed a more florid fibrocellular response, as in human coronary arteries, with cell proliferation initially confined to areas with dedifferentiated SMCs in the preexistent media and, once neointimal tissue was formed, among spindle cells also. The similarities with the repair processes encountered in postangioplasty human coronary arteries suggest that the WHHL rabbit is an adequate model to study differences in the response related to different types of angioplasty injury.

Upregulation of angiotensin-converting enzyme during the healing process after injury at the site of percutaneous transluminal coronary angioplasty in humans

BACKGROUND

Balloon injury models in rat have shown enhanced expression of ACE in the developing neointima. However, neointimal lesions in human coronary arteries are complex due to atherosclerosis and different types of wall laceration. This study was designed to investigate whether ACE is present in the neointima of humans, including patients with restenosis after percutaneous transluminal coronary angioplasty (PTCA).

METHODS AND RESULTS

Thirty-seven sites with angioplasty injury, obtained at autopsy, were studied using immunocytochemical techniques. Sites with injury limited to a fibrous plaque and those with injury extending into the media (<2 months after PTCA) showed fibrocellular repair tissue composed mainly of smooth muscle cells that were distinctly positive for ACE. In cellular reactions at the site of injury limited to the atheromatous plaque (<2 months after PTCA), the expression of ACE appeared first in accumulated macrophages; once smooth muscle cells appeared in the repair tissue, they also expressed ACE. At a later stage (3 months after PTCA), the number of cells with ACE expression decreased markedly; from 7 months on, ACE was no longer expressed within the repair tissue. Basically, there were no differences with regard to ACE expression during the healing process after PTCA between segments with and those without angiographic evidence of restenosis.

CONCLUSIONS

These results show that PTCA injury in humans results in upregulation of ACE at sites of active repair and, therefore, ACE could play an important role as one of the mediators of the healing process after PTCA.

Selective deposits of versican in the extracellular matrix of restenotic lesions from human peripheral arteries

Although a large percentage of the volume of human restenotic arterial lesions is occupied by extracellular matrix (ECM), the composition and organization of this ECM are not well characterized. In this study, restenotic segments taken from 30 human peripheral arteries by directional atherectomy at times ranging from 13 days to 36 months after angioplasty were analyzed for specific patterns of ECM composition and organization by light and electron microscopic histochemistry and immunohistochemistry. Histochemical analysis revealed the presence of distinct zones, enriched either in proteoglycans or fibrillar collagen. Most sections contained these regions juxtaposed to each other. The frequency of these two distinct ECMs did not change as a function of time after angioplasty. The collagen-rich zone usually contained elongated smooth muscle cells spaced close together except in regions resembling fibrous plaques. The proteoglycan-rich ECM contained both elongated and stellate-shaped smooth muscle cells randomly arranged and separated by wide distances. This region resembled the loose-connective-tissue-containing myxoid region typical of restenotic lesions. Immunohistochemical analysis of these regions revealed that the proteoglycan-containing zone stained intensely for versican, a large interstitial chondroitin sulfate proteoglycan, whereas the collagen-containing areas were mostly negative for versican but positive for type I collagen. The versican-positive regions also immunostained for biglycan, a small leucine-rich dermatan sulfate proteoglycan, and sparsely for elastin. However, both of these ECM molecules were present in the versican-negative type I collagen-positive regions of the lesions. These results suggest that the development of restenotic lesions involves localized deposits of specific ECM molecules that may play a role in the asymmetric renarrowing of this tissue after angioplasty.

Redifferentiation of smooth muscle cells after coronary angioplasty determined via myosin heavy chain expression

BACKGROUND

The pathophysiology of phenotypic modulation of smooth muscle cells (SMCs) involved in restenosis after angioplasty is not well understood. Smooth muscle myosin heavy chain (SM MHC) isoforms (SM1 and SM2) are specific markers for SMC differentiation. In particular, SM2 is useful as a marker of mature SMCs. SMemb is a nonmuscle myosin heavy chain (NM MHC) whose expression is upregulated in immature or activated SMC.

METHODS AND RESULTS

To determine SMC phenotypes in neointimal tissues after percutaneous transluminal coronary angioplasty (PTCA), we performed immunohistochemistry on human coronary arteries with antibodies against alpha-SM actin, SM1, SM2, and SMemb. Tissues were obtained from six autopsied patients and from atherectomy specimens from 16 patients who had undergone PTCA. Medial SMCs were positive for alpha-actin, SM1, and SM2. Expression of SM1 and SM2 in the neointima varied with the time after intervention, whereas alpha-actin was constitutively expressed in all cases studied. Neointimal cells at 16 and 20 days after PTCA contained alpha-actin but little or no SM1 or SM2, indicating that these cells modulated their phenotype to the immature state. Neointimal SMCs recovered SM MHC expression, first SM1 and then SM2, by 6 months after PTCA. Increased expression of SMemb was found in the neointima but without apparent relationship to the time after PTCA.

CONCLUSIONS

Neointimal SMCs show features of an undifferentiated state, indicated by altered expression of SM MHC, and undergo redifferentiation in a time-dependent manner. The expression of SM MHC isoforms provides insight into the biology of healing after angioplasty and furnishes useful tools for the understanding of the roles of differentiation and phenotypic modulation of SMCs in human vascular lesions.

Coronary artery and saphenous vein graft remodeling: A review of histologic findings after various interventional procedures--Part III

Catheter balloon angioplasty is a well accepted form of nonsurgical treatment of acutely and chronically obstructed coronary artery vessels. It is also the centerpiece for various new intervention techniques. Their morphologic effects on the site of obstruction has been termed "remodeling." Part III of this six-part series focuses on intimal proliferation and chronic recoil in patients undergoing previous remodeling techniques by balloon angioplasty.

In situ detection of platelet-derived growth factor-A and -B chain mRNA in human coronary arteries after percutaneous transluminal coronary angioplasty

Experimental studies have shown that platelet-derived growth factor (PDGF) plays a role in wound-healing processes after angioplasty. In humans, after percutaneous transluminal coronary angioplasty (PTCA), this has not yet been documented. Six coronary arteries of five patients who died after PTCA were studied. The angioplasty sites were sliced serially, and the slices were studied using immunocytochemistry and in situ hybridization. Monoclonal antibodies were directed against muscle actin, vimentin, macrophages, and endothelium. In situ hybridization was performed using a synthetic oligonucleotide probe complementary to the PDGF-A and -B chain mRNAs. The identification of cells was based on a comparison with immune-stained sections. Positive autoradiographic signals for PDGF-A and -B chain mRNAs were found at the site of the PTCA injury and related to areas that contained macrophages, spindle cells, smooth muscle cells, and endothelial cells of neovascularization. In humans, both PDGF-A and -B chain mRNAs are expressed at sites of PTCA injury. The expression relates to the reparative response, and it appears that the cells involved are macrophages, spindle cells, smooth muscle cells, and endothelial cells of neovascularization. This is the first study to document the expression of PDGF-A and -B mRNAs at sites of repair in human coronary arteries after PTCA. It suggests strongly that PDGF is involved in the repair process after PTCA.

Arterial remodeling after coronary angioplasty: a serial intravascular ultrasound study

BACKGROUND

Restenosis occurs after 30% to 50% of transcatheter coronary procedures; however, the natural history and pathophysiology of restenosis are still incompletely understood.

METHODS AND RESULTS

Serial (postintervention and follow-up) intravascular ultrasound imaging was used to study 212 native coronary lesions in 209 patients after percutaneous transluminal coronary angioplasty, directional coronary atherectomy, rotational atherectomy, or excimer laser angioplasty. The external elastic membrane (EEM) and lumen cross-sectional areas (CSA) were measured; plaque plus media (P+M) CSA was calculated as EEM minus lumen CSA. The anatomic slice selected for serial analysis had an axial location within the target lesion at the smallest follow-up lumen CSA. At follow-up, 73% of the decrease in lumen (from 6.6+/-2.5 to 4.0+/-3.7 mm2, P<.0001) was due to a decrease in EEM (from 20.1+/-6.4 to 18.2+/-6.4 mm2, P<.0001); 27% was due to an increase in P+M (from 13.5+/-5.5 to 14.2+/-5.4 mm2, P<.0001). Delta Lumen CSA correlated more strongly with delta EEM CSA (r=.751, P<.0001) than with delta P+M CSA (r=.284, P<.0001). Delta EEM was bidirectional; 47 lesions (22%) showed an increase in EEM. Despite a greater increase in P+M (1.5+/-2.5 versus 0.5+/-2.0 mm2, P=.0009), lesions exhibiting an increase in EEM had (1) no change in lumen (-0.1+/-3.3 versus 3.6+/-2.3 mm2, P<.0001), (2) a reduced restenosis rate (26% versus 62%, P<.0001), and (3) a 49% frequency of late lumen gain (versus 1%, P<.0001) compared with lesions with no increase in EEM.

CONCLUSIONS

Restenosis appears to be determined primarily by the direction and magnitude of vessel wall remodeling (delta EEM). An increase in EEM is adaptive, whereas a decrease in EEM contributes to restenosis.

Expression of platelet derived growth factor B chain and beta receptor in human coronary arteries after percutaneous transluminal coronary angioplasty: an immunohistochemical study

OBJECTIVE

To evaluate whether expression of platelet derived growth factor B (PDGF-B) protein is associated with expression of its receptor protein in human coronary arteries after angioplasty and to identify cells involved.

BACKGROUND

PDGF is considered an important growth factor in the repair process of the vessel wall after angioplasty. In situ hybridisation has revealed expression of PDGF-A and -B chain messenger ribonucleic acid (mRNA) in human coronary arteries at sites of postangioplasty injury.

METHODS

Target and non-target sites of eight coronary arteries were studied immunohistochemically for PDGF-B and PDGF-beta receptor proteins in relation to macrophages, T lymphocytes, smooth muscle cells, and HLA-DR positive cells.

RESULTS

The PDGF-B and PDGF-beta receptor proteins were expressed in areas with distinct repair, containing alpha actin negative spindle cells, macrophages and, at later stages, alpha actin positive smooth muscle cells as well. When the neointima was composed mainly of alpha actin smooth muscle cells, PDGF-B expression was rare and PDGF-beta receptor expression was negative.

CONCLUSIONS

There is expression of PDGF-B and PDGF-beta receptor proteins at sites of postangioplasty repair in human coronary arteries. The associated cells are mainly macrophages and alpha actin negative spindle cells; the latter may be dedifferentiated smooth muscle cells. A link between PDGF expression and the postangioplasty time interval suggests a relation with cell differentiation as part of the maturation of the repair tissue. Mutual expression of both the growth factor and its receptor protein strongly suggests that in humans a PDGF mediated repair process occurs, with involvement of smooth muscle cells and macrophages.

Apoptosis in human atherosclerosis and restenosis

BACKGROUND

Apoptosis has been recognized in normal, including rapidly proliferating, cell populations and is inferred to be potentially responsible for the maintenance of stable cell numbers in tissues with various degrees of proliferative activity. Previous studies performed in rats indicated that despite the persistence of a relatively high level of injury-induced proliferative activity, total arterial smooth muscle content at 12 weeks remained unchanged from that measured at 2 weeks, suggesting that accrual of vascular smooth muscle cells is mitigated by cell death. The extent to which apoptosis may be observed in human atherosclerosis and/or restenosis, however, has not been previously established.

METHODS AND RESULTS

We performed immunohistochemical studies on 56 specimens retrieved from patients undergoing directional atherectomy for primary atherosclerotic lesions or recurrent arterial narrowing after percutaneous revascularization (restenosis). Immunohistochemical staining disclosed evidence of apoptosis in 35 (63%) of the 56 specimens studied. When present, immunohistochemical evidence of apoptosis was typically limited to < 2% of cells in the specimen. The finding of apoptosis, however, was not distributed equally among four groups of specimens studied. Specimens retrieved from patients with restenosis were more frequently observed to contain foci of apoptosis than specimens retrieved from patients with primary atherosclerotic lesions. Among 14 peripheral arterial specimens from patients with restenosis, 13 (93%) contained foci of apoptosis; in contrast, apoptosis was observed in only 6 (43%) of 14 peripheral specimens from patients with primary lesions (P = .0046). Among coronary arterial specimens, apoptosis was observed in 12 (86%) of 14 specimens from patients with restenosis versus 6 (29%) of 14 specimens from patients with primary obstructions (P < .0075).

CONCLUSIONS

Apoptosis is a feature of human vascular pathology, including restenotic lesions and, to a lesser extent, primary atherosclerotic lesions. The findings of the present study suggest that apoptosis may modulate the cellularity of lesions that produce human vascular obstruction, particularly those with evidence of more extensive proliferative activity.

Corticosteroid agents inhibit proliferation of smooth muscle cells from human atherosclerotic arteries in vitro

We studied the in vitro effect of steroid agents on smooth muscle cells from human atherosclerotic arteries. Recent advances in the understanding of the biology of restenosis indicate that restenosis is predominantly caused by a multifactorial stimulation of smooth muscle cell proliferation. Primary stenosing plaque material of 24 patients (aged 63 +/- 14 years) and restenosing plaque material of 7 patients (aged 65 +/- 9 years) was selectively extracted from femoral arteries by the Simpson atherectomy device. Cells were isolated by enzymatic disaggregation and identified as smooth muscle cells by positive reaction with smooth muscle alpha-actin. The steroid agents prednisolone (0.0075-750 micrograms/ml), hydrocortisone (0.0125-1250 micrograms/ml), and dexamethasone (0.0004-40 micrograms/ml) were added to the cultures. Six days after seeding the cells were trypsinized and the cell number was measured by a cell counter. All three steroid agents exhibited a significant antiproliferative effect on smooth muscle cell proliferation. At high concentrations of hydrocortisone, cytoskeletal elements of smooth muscle cells such as actin, microtubules, and vimentin, were largely altered. Our data indicate that the proliferation of smooth muscle cells from human atherosclerotic arteries in vitro can be inhibited by steroid agents and thus may open the way for local post-angioplasty treatment strategies.

Is the Watanabe heritable hyperlipidemic rabbit a suitable experimental model for percutaneous transluminal coronary angioplasty in humans? A light microscopic, immunohistochemical and ultrastructural study

OBJECTIVES

This study was designed to assess an experimental model for the study of mechanisms that underlie restenosis after percutaneous transluminal coronary angioplasty.

BACKGROUND

The Watanabe heritable hyperlipidemic (WHHL) rabbit lacks the receptor for low density lipoproteins, produces atherosclerotic lesions very similar to those in humans and, therefore, could serve as a suitable model.

METHODS

Percutaneous transluminal angioplasty was performed on the left subclavian artery of 10 homozygous rabbits. The animals were killed at a few hours or 3, 7, 14 or 28 days after the procedure. The artery was fixed by perfusion, and the site of angioplasty was examined by both light and electron microscopy with the use of conventional and immunohistochemical staining techniques.

RESULTS

Angioplasty had caused a flap-like or dissecting tear into the media. At day 3, cells within the preexisting media adjacent to the injury had the ultrastructural characteristics of synthetic smooth muscle cells. At day 7, spindle cells at the site of injury stained either negative or very weakly positive with a marker for actin; ultrastructurally, these cells had the synthetic phenotype. At day 14, the spindle cells showed a mix of contractile and synthetic phenotypes. The surface was partially covered by endothelial cells. At day 28, the dominant cell type was the contractile smooth muscle cell and the surface was completely covered by endothelial cells.

CONCLUSIONS

Both the injury and the response to injury after percutaneous transluminal angioplasty were almost identical to that seen in humans after coronary angioplasty. Thus, the WHHL rabbit appears to be an appropriate experimental model for use in further studies.

Pathophysiological mechanisms for restenosis following coronary angioplasty: possible preventive alternatives

Restenosis after successful percutaneous transluminal coronary angioplasty (PTCA) remains an unsolved medical problem. The search for the underlying pathophysiological mechanisms have identified intimal proliferation of smooth muscle cells (SMC) to be the prevailing cause of late restenosis, with endothelial cells (EC) and platelets being important participators in the process. According to the most accepted present theory, SMC would be stimulated to migrate and proliferate shortly after the angioplasty by the release of growth factors from injured EC and accumulated platelets. However, clinical trials of agents interfering with these mechanisms have not significantly diminished the rate of restenosis, which suggest both that our knowledge of the process is incomplete, and that new ways of administering the agents may be required.

SIN-1 reduces platelet adhesion and platelet thrombus formation in a porcine model of balloon angioplasty

BACKGROUND

Nitric oxide inhibits platelet adhesion and platelet aggregation in vivo. In this study, we investigated the effects of the nitric oxide donor SIN-1 on platelet adhesion and platelet-thrombus formation following experimental angioplasty.

METHODS AND RESULTS

Bilateral carotid angioplasty was performed in 20 anesthetized pigs. Animals received either SIN-1 (3-morpholino-sydnonimine; 10 micrograms/kg/min; n = 8) or placebo (n = 8) before and during angioplasty. An additional control group of pigs received trimetaphan (n = 4), which induced hemodynamic changes similar to those that followed treatment with SIN-1. Platelet deposition was quantified by the injection of autologous 111In-labeled platelets. SIN-1 reduced platelet deposition after deep arterial injury compared with placebo (mean +/- SEM, 10.870 +/- 2.415 versus 40.326 +/- 9.889 platelets x 10(6)/cm2, p < 0.05). SIN-1 reduced platelet adhesion after superficial injury compared with both placebo and trimetaphan (2.231 +/- 0.333 versus 5.278 +/- 0.606 versus 5.022 +/- 1.136 platelets x 10(6)/cm2, respectively; p < 0.005). Scanning electron microscopy confirmed that platelets were deposited in the form of an adherent monolayer following superficial endothelial denudation and were reduced in number following treatment with SIN-1. The effects of SIN-1 on platelet function were associated with a significant increase in platelet cyclic GMP concentration from baseline (3.15 +/- 0.88 versus 1.58 +/- 0.73 pmol/10(9) platelets, p < 0.005).

CONCLUSIONS

SIN-1 reduces platelet adhesion and platelet-thrombus formation following experimental angioplasty. The antiadhesive effects of SIN-1 are independent of changes in systemic hemodynamics. These results imply that the administration of a nitric oxide donor may prove effective in modifying the pathophysiological response to angioplasty injury.

Contained rupture following percutaneous transluminal coronary angioplasty: long-term outcome

Coronary artery aneurysm formation can occur as a complication of balloon angioplasty. We present a case of a contained rupture of the left circumflex artery following angioplasty which resulted in an unusual pseudoaneurysm on angiography at 3-year follow-up.

In vitro effects of a recombinant toxin targeted to the fibroblast growth factor receptor on rat vascular smooth muscle and endothelial cells

The dominant mechanism responsible for restenosis after angioplasty is believed to be the activation of medial smooth muscle cells (SMCs), leading to their proliferation, migration to the subintima, and further proliferation. To develop novel strategies that might inhibit or prevent restenosis, we previously used a chimeric toxin composed of transforming growth factor-alpha (which targets the epidermal growth factor receptor) and mutated Pseudomonas exotoxin to preferentially recognize and kill rapidly proliferating, versus quiescent, vascular SMCs. We have recently cloned and expressed a recombinant gene encoding Pseudomonas exotoxin with a mutated (nonfunctional) cell recognition domain fused with the ligand acidic fibroblast growth factor, termed aFGF-PE66(4Glu)KDEL; thus, this recombinant toxin targets the fibroblast growth factor receptor. In the present study, we evaluated the relative effects of this chimeric toxin on quiescent versus rapidly proliferating vascular SMCs and also determined whether aFGF-PE66(4Glu)KDEL exerted different effects on SMCs versus endothelial cells. Rapidly proliferating SMCs (grown in 10% fetal bovine serum) were very sensitive to the cytotoxic effects of aFGF-PE66(4Glu)KDEL, whereas cytotoxicity was significantly less when the SMCs were in a quiescent state (grown in medium supplemented with 0.5% fetal bovine serum). The chimeric toxin was also significantly less cytotoxic against endothelial cells. Competition studies using excess acidic fibroblast growth factor indicated that the cytotoxic effects are specifically mediated by the fibroblast growth factor receptor. Thus, the present studies suggest a potentially expanded role of recombinant toxin therapy in restenosis: multiple receptors can be targeted, and cytotoxic effects, at least in vitro, can be preferentially directed to rapidly proliferating vascular SMCs, with relative sparing of vascular endothelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary intimal proliferation after balloon injury and stenting in swine: an animal model of restenosis

OBJECTIVES

This study was designed to compare the proliferative response in coronary arteries after tantalum stent placement or balloon injury in a normolipemic swine model of restenosis.

BACKGROUND

Restenosis remains a significant complication of percutaneous transluminal coronary angioplasty. Efforts to study restenosis have been hampered by the lack of a suitable animal model.

METHODS

In an attempt to create lesions resembling those of human restenosis, normolipemic swine underwent injury of either the left anterior descending or the left circumflex coronary artery with either balloon inflation or deployment of a tantalum stent. At 4 weeks, they were killed and the injured vessels processed for histopathologic analysis. Intimal area, lumen area and maximal intimal thickness were measured. The degree of stenosis was expressed as residual lumen area (lumen area/intimal area ratio).

RESULTS

Vessels injured by either method demonstrated significant intimal smooth muscle proliferation leading to reduction in lumen area. In the 18 stented vessels residual lumen area measured 0.64 +/- 0.18 and maximal intimal thickness measured 0.6 +/- 0.3 mm; in the 15 balloon-injured vessels these values were 0.75 +/- 0.18 and 0.4 +/- 0.3 mm, respectively (p less than 0.05). In addition, most stented vessels had reactive inflammatory infiltrates surrounding the stent wires composed of lymphocytes, histiocytes and many eosinophils.

CONCLUSIONS

These data indicate that coronary artery injury in swine with either balloon inflation or stenting leads to intimal smooth muscle cell proliferation similar to that seen in human restenosis. The degree of intimal proliferation appears to be greater after stenting than after balloon injury. Intracoronary stenting in swine is associated with a marked inflammatory reaction around the stent wires. These models may be helpful in planning systemic and local antirestenosis strategies.

Hereditary heparin cofactor II deficiency and coronary artery disease

We here present a Japanese family with type I hereditary heparin cofactor II (HC II) deficiency. The propositus (a 61-year-old man) suffered from angina pectoris and coronary artery disease was confirmed by coronary angiography. He underwent percutaneous transluminal coronary angioplasty (PTCA) four times in one year. Combined use of heparin, aspirin, and nitrates could not prevent the return of his symptoms and restenosis of segment 6 of the left anterior descending artery. His HC II activity and antigen levels were 49% and 50%, respectively, and his daughter also showed similar low levels. Cerebral infarction had occurred in two family members. Argatroban, a selective potent thrombin inhibitor, was administered after the fourth PTCA for the purpose of preventing reocclusion and achieved a successful outcome. A relationship between HC II deficiency and thrombosis has not yet been established. Our case suggests that standard heparin therapy is not effective in preventing restenosis in such individuals, in whom the process is accelerated by thrombin generation at the site where PTCA produces rupture of the atherosclerotic plaque. Argatroban may be more effective under low HC II conditions because of its potent inhibition of thrombin activity at sites of vascular wall damage.

Direct intraarterial wall injection of microparticles via a catheter: a potential drug delivery strategy following angioplasty

Local delivery into the arterial wall of medications at high concentrations may evolve as a method to reduce postangioplasty restenosis. However, since the atherosclerotic artery has increased vasa vasorum, medications injected in a fluid state may diffuse out of the arterial wall too quickly to have a therapeutic effect. Thus we evaluated whether microparticles as a model for a particulate microcarrier drug delivery system, injected via a porous balloon catheter, could be retained within the atherosclerotic rabbit femoral arterial wall. Arteries were injected with a 5 microns microparticle suspension for 45 seconds at either 3 or 5 atm of infusion pressure immediately following balloon angioplasty. Arteries were obtained immediately following the procedure or at 1, 3, 7, or 14 days after infusion to evaluate for the presence of retained microparticles. Of 34 arteries, 30 contained retained microparticles, with 21 exhibiting microparticles in the neointimia, 12 in the media, and 25 in the adventitia. Microparticles were retained for as long as 14 days, and there was no difference between the distribution or quantity of microparticles at 3 or 5 atm of infusion pressure. The mode of microparticle distribution probably involved deposition within dissection planes, although evidence for vasa vasorum transport was observed. We hypothesize that biodegradable microparticles could serve as a vehicle for intramural drug delivery in the treatment of restenosis.

Use of a morphologic classification to predict clinical outcome after dissection from coronary angioplasty

To determine if morphology of procedure-associated dissections could help predict clinical outcome, angiograms of 691 coronary artery dissections resulting from percutaneous transluminal coronary angioplasty were categorized according to the National Heart, Lung, and Blood Institute classification system. Classes of dissection were then correlated with clinical outcome: 543 patients with type B dissections had no increase in morbidity and mortality when compared with patients without dissection, with a similar success rate of 93.7%. Complications in this group were low and compared favorably with complication rates in procedures not associated with dissection. One hundred forty-eight procedures associated with dissections of types C to F had a significant increase in in-hospital complications, including acute closure (31%), need for emergency coronary bypass surgery (37%), myocardial infarction (13%) and repeat angioplasty (24%). The overall clinical success rate for those with types C to F dissection was 38%. The differences in clinical success and acute complications between type B and types C to F dissections were statistically significant at p less than 0.0005 for all variables studied. The angiographic morphology of a dissection during coronary angioplasty can predict clinical outcome, aiding in selection of effective therapy.

The role of platelets, thrombin and hyperplasia in restenosis after coronary angioplasty

Coronary angioplasty has become a successful and widely used treatment for patients with coronary artery disease since its first clinical application in 1977. The primary success rate has improved despite the increase in procedure and case complexity. However, acute reocclusion and late restenosis, which constitute the most important problems after successful angioplasty, continue to occur in about 5% and 35% of patients within 3 to 6 months, respectively. Angioscopic and pathologic observations have suggested that a multifactorial pathophysiologic process accounts for acute reocclusion, involving marked thrombosis, intimal dissection, medial and subintimal hemorrhage, vascular recoil and vasocontriction. In contrast, chronic restenosis involves the development of fibrocellular intimal hyperplasia within a milieu created by vascular injury, platelet activation, thrombin generation and the release of mitogens. Although current pharmacologic approaches, which involve antithrombotic and anticoagulant therapy, have been largely ineffective in eliminating acute reocclusion and chronic restenosis, recent advances in the research in thrombosis, platelet receptors and smooth muscle growth regulation have allowed new therapeutic options to be tested in the experimental setting, with subsequent potential clinical applications in patients.

Restenosis 1 to 24 months after clinically successful coronary balloon angioplasty: a necropsy study of 20 patients

This report describes clinical, morphologic and histologic findings at necropsy late (range 1.6 to 24.1 months [average 8.2 months]) after clinically successful coronary balloon angioplasty in 20 patients with coronary angioplasty restenosis. Clinical evidence of restenosis occurred in 14 patients (70%), including 6 patients with sudden coronary death. Of the 20 patients, 14 (70%) had a cardiac cause of death and 6 (30%) had a noncardiac cause of death. Two major subgroups of histologic findings were observed: 1) intimal proliferation (60%), and 2) atherosclerotic plaque only (40%). Of the eight sites with atherosclerotic plaque only, six were eccentric lesions and two were concentric lesions. No morphologic evidence of previous angioplasty injury (cracks, breaks, tears) was observed in the eight patients with atherosclerotic plaque only. Proposed mechanisms for the development of intimal proliferation involve the reaction of smooth muscle cells and platelets, whereas elastic recoil of overstretched eccentric or concentric atherosclerotic lesions represents the most likely explanation for the findings in the latter subgroup. On the basis of these morphologic findings at angioplasty restenosis sites, specific treatment strategies for restenosis after coronary artery balloon angioplasty are proposed.

Fibrocellular tissue response after percutaneous transluminal coronary angioplasty. An immunocytochemical analysis of the cellular composition

BACKGROUND

Restenosis after initial, successful percutaneous transluminal coronary angioplasty (PTCA) is due to fibrocellular proliferation.

METHODS AND RESULTS

The present study focused on the nature of fibrocellular tissue in humans by use of immunocytochemical techniques. Four hearts (five coronary arteries) were investigated; time lapse between PTCA and death varied between 20 days (two arteries) and 1 year 7 months. Proliferating cells stained positive with smooth muscle cell-specific monoclonal antibodies. Cells from early proliferative lesions (20 days) have a phenotypic expression different from cells in "old" lesions. Proliferating cells stained positive with vimentin but were negative with desmin, irrespective of the lesion's age.

CONCLUSIONS

The findings indicate a change in actin isoform expression of smooth muscle cells while adapting to a pathological state.

A paradigm for restenosis based on cell biology: clues for the development of new preventive therapies

Angioplasty causes substantial injury to the coronary artery intima and media that is unrecognizable by angiography. On the basis of a substantial body of research in oncology and wound healing, it is hypothesized that restenosis is a manifestation of the general wound healing response expressed specifically in vascular tissue. The temporal response to injury occurs in three characteristic phases: inflammation, granulation and extracellular matrix remodeling. The specific expression of these phases in the coronary artery leads to intimal hyperplasia at 1 to 4 months. The major milestones in the temporal sequence of restenosis are platelet aggregation, inflammatory cell infiltration, release of growth factors, medial smooth muscle cell modulation and proliferation, proteoglycan deposition and extracellular matrix remodeling. Each step has potential inhibitors that could be used for preventive therapy. Resolution of restenosis, however, probably requires both creation of the largest possible residual lumen and substantial inhibition of intimal hyperplasia.

Differential histopathology of primary atherosclerotic and restenotic lesions in coronary arteries and saphenous vein bypass grafts: analysis of tissue obtained from 73 patients by directional atherectomy

Vascular tissue obtained using a directional percutaneous atherectomy device was examined microscopically. Tissue was obtained from coronary arteries without prior instrumentation (primary lesions, n = 31), aortocoronary saphenous vein bypass grafts with primary lesions (n = 8), coronary arteries with lesions developing after prior balloon angioplasty or mechanical atherectomy (restenotic lesions, n = 30) and vein bypass grafts with restenotic lesions (n = 4). Primary lesions were characterized by dense intimal fibrosis with necrotic debris (83% of intimal tissue) and foam cells typical of atherosclerosis. These lesions frequently contained cholesterol crystals (45% of coronary arteries, 50% of vein grafts) and calcium deposits (65% of coronary arteries, 38% of vein grafts). Restenotic lesions were characterized by an increased proportion of loose fibroproliferative tissue (45% of coronary artery intima, 35% of vein graft intima). Immunohistochemical stains confirmed this proliferative tissue to be primarily smooth muscle cells. Thrombus was rarely observed. Comparison of resected tissues indicated that dense fibrosis and necrosis are significantly more common in primary than in restenotic lesions (83% versus 56% of intimal tissue, p = 0.0005), whereas smooth muscle cell hyperplasia is more common in restenotic than in primary lesions (44% versus 17% of intimal tissue, p less than 0.0005). Partial-thickness resection of medial tissue or full-thickness resection of media with associated adventitial tissue occurred in 27 (56%) of 39 primary atheromatous lesions and 16 (47%) of 34 restenotic lesions; subintimal tissue obtained from primary lesions appeared identical to that obtained from restenotic lesions. These data indicate that the histopathologic characteristics of the neointimal layer of restenotic lesions differ from those of the intimal layer of primary atherosclerotic lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Lesions in side branches of arteries having undergone percutaneous transluminal coronary angioplasty: a histopathologic study

Percutaneous transluminal coronary angioplasty (PTCA) may cause occlusion in side branches. No histologic studies, however, have been made on side branches of the arteries in which PTCA has been performed. A histologic study was therefore made to explain the effect of PTCA on side branches. Histologic specimens were prepared by serial step sectioning from 15 side branches of 10 autopsied cases that had undergone PTCA. The results of examination by light microscope were as follows: (1) Stenoses due to PTCA were seen in seven branches (46.7%). (2) The stenoses were classified into three types: (a) stenosis due to blocking of the orifice of a side branch by the disrupted portion of the intima of the main artery (one branch); (b) stenosis due to medial dissection of the main artery or further dissection occurring even in the side branches (three branches); and (c) stenosis due to fragmentation of the internal elastic lamina of the main artery accompanied by proliferation of smooth muscle cells even in the side branch (three branches). It is now clear that stenosis is caused in side branches long after PTCA. Extra care is required when major side branches exist in the portion where this procedure is to be performed.

Laser ablation and the need for intra-arterial imaging

In 48 patients with severe claudication due to a total obstruction of the femoropopliteal artery, percutaneous recanalization was attempted with a 2.2 mm diameter rounded sapphire contact probe in conjunction with a continuous wave Nd:YAG laser. In eight patients the contact probe laser catheter took a subintimal course that could not be redressed. Laser recanalization needs high-resolution diagnostic information on the complex anatomy of the obstruction. Intra-arterial ultrasound imaging may provide the necessary information to evaluate, monitor or guide novel angioplasty techniques. The design of an ultrasound catheter which combines high-resolution diagnostic imaging with steerability, flexibility and controlled ablation is now the major engineering challenge in interventional cardiology.